Connecting the microscopic depolarizing origin of samples with macroscopic measures of the Indices of Polarimetric Purity

In this work we show how a specific set of three depolarizing observables, the Indices of Polarimetric Purity (IPP), P1, P2 and P3, are ideal metrics to study the depolarization characteristic of media. We simulate different depolarizing scenarios, based on different depolarizing origins, and we study the corresponding IPP values. The simulations are based on the incoherent addition of multiple elemental polarizing elements, as ideal polarizers and/or retarders with different specific characteristics (orientation, retardance, transmittance, etc.). Further depolarizing scenarios are also studied by including the effect of ideal depolarizers. We show for the first time how by analyzing depolarizing systems through IPP we unravel two different depolarizing origins: isotropic and anisotropic depolarization, with meaningful physical interpretation. The former, isotropic depolarization is related to pure scattering processes, and mainly connected with P3 observable. The later, anisotropic depolarization is originated by microscopic constituent elements showing polarimetric anisotropy (dichroic and/or birefringent elements with different characteristics) and anisotropic scattering produced by these elements, and mainly described by P1 and P2 observables. Both effects can be simultaneously observed in real samples and give us information of the processes that give rise to depolarization in light-matter interactions. The simulated results are experimentally validated by analyzing the depolarizing behavior, in terms of IPP, of diverse real samples with easy physical interpretation, and direct connection with simulations. The present study could be of interest in multiple scenarios, to further understand the depolarizing response of samples, and it can be of special interest for the study of biological tissues and pathologies, as they present important depolarizing behavior.Monica Canabal-Carbia reports financial support was provided by Spain Ministry of Science and Innovation (PID2021-560 126509OB-C21 and PDC2022-133332-C21). Juan Campos reports financial support was provided by Spain Ministry of Science and Innovation (PID2021-560 126509OB-C21 and PDC2022-133332-C21). Angel Lizana reports financial support was provided by Spain Ministry of Science and Innovation (PID2021-560 126509OB-C21 and PDC2022-133332-C21). Irene Estevez reports financial support was provided by Government of Catalonia (Beatriu de Pinos, 2021-BP-00206). Ignacio Moreno reports financial support was provided by Spain Ministry of Science and Innovation (PID2021-126509OB-C22). Andres Marquez reports financial support was provided by Government of Valencia. Andres Marquez reports financial support was provided by Spain Ministry of Science and Innovation ( PID2021-123124OB-I00). Esther Nabadda reports financial support was provided by Government of Valencia. Mónica Canabal-Carbia, Angel Lizana and Juan Campos reports financial support was provided by the Generalitat de Catalunya (2021SGR00138)

Low-level viraemia: An emerging concern among people living with HIV in Uganda and across sub-Saharan Africa.

Attaining viral load (VL) suppression for over 95% of the people living with HIV on antiretroviral therapy is a fundamental step in enabling Uganda and other sub-Saharan African countries to achieve global Sustainable Development Goal targets to end the HIV/AIDS epidemic by 2030. In line with the 2013 World Health Organization recommendations, several sub-Saharan African countries, including Uganda, use a threshold of 1000 HIV viral RNA copies/mL to determine HIV viral non-suppression. The United States Centers for Disease Control and Prevention and the International Association of Providers of AIDS Care deem this threshold very high, and hence recommend using 200 copies/mL to determine viral non-suppression. Using 1000 copies/mL as a threshold ignores people living with HIV who have low-level viraemia (LLV; HIV VL of at least 50 copies/mL but less than 1000 copies/mL). Despite the 2021 World Health Organization recommendations of using intensive adherence counselling for people living with HIV with LLV, several sub-Saharan African countries have no interventions to address LLV. However, recent studies have associated LLV with increased risks of HIV drug resistance, virologic failure and transmission. The purpose of this narrative review is to provide insights on the emerging concern of LLV among people living with HIV receiving antiretroviral therapy in sub-Saharan Africa. The review also provides guidance for Uganda and other sub-Saharan African countries to implement immediate appropriate interventions like intensive adherence counselling, reducing VL thresholds for non-suppression and conducting more research to manage LLV which threatens progress towards ending HIV by 2030

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Experimental evaluation of Fourier transform holograms by a self-interferometric technique

We present a technique that combines an encoding method to display complex-valued holograms onto a phase-only spatial light modulator (SLM) with a phase-shifting interferometric (PSI) technique for experimentally evaluating the generated complex-valued optical fields. We demonstrate an efficient common-path polarization interferometer based on the SLM itself, not requiring any external additional element. The same setup can be used to simultaneously display the complex hologram and to apply the phase-shifting values required to retrieve the phase distribution of the optical field. A simple rotation of a polarizer allows to change from the intensity configuration to the interferometer configuration

The association between low-level viraemia and subsequent viral non-suppression among people living with HIV/AIDS on antiretroviral therapy in Uganda.

BackgroundUganda's efforts to end the HIV epidemic by 2030 are threatened by the increasing number of PLHIV with low-level viraemia (LLV). We conducted a study to determine the prevalence of LLV and the association between LLV and subsequent viral non-suppression from 2016 to 2020 among PLHIV on ART in Uganda.MethodThis was a retrospective cohort study, using the national viral load (VL) program data from 2016 to 2020. LLV was defined as a VL result of at least 50 copies/ml, but less than 1,000 copies/ml. Multivariable logistic regression was used to determine the factors associated with LLV, and cox proportional hazards regression model was used to determine the association between LLV and viral non-suppression.ResultsA cohort of 17,783 PLHIV, of which 1,466 PLHIV (8.2%) had LLV and 16,317 (91.8%) had a non-detectable VL was retrospectively followed from 2016 to 2020. There were increasing numbers of PLHIV with LLV from 2.0% in 2016 to 8.6% in 2020; and LLV was associated with male sex, second line ART regimen and being of lower age. 32.5% of the PLHIV with LLV (476 out of 1,466 PLHIV) became non-suppressed, as compared to 7.7% of the PLHIV (1,254 out of 16,317 PLHIV) with a non-detectable viral load who became non-suppressed during the follow-up period. PLHIV with LLV had 4.1 times the hazard rate of developing viral non-suppression, as compared to PLHIV with a non-detectable VL (adjusted hazard ratio was 4.1, 95% CI: 3.7 to 4.7, p ConclusionOur study indicated that PLHIV with LLV increased from 2.0% in 2016 to 8.6% in 2020, and PLHIV with LLV had 4.1 times the hazard rate of developing viral non-suppression, as compared to PLHIV with a non-detectable VL. Hence the need to review the VL testing algorithm and also manage LLV in Uganda